This invention relates to tire pressure sensing systems.
The invention is particularly, but not exclusively concerned with systems for sensing the pressure of tires on aircraft wheels.
Aircraft wheel tires are subjected to high rotational speeds and heavy loading, especially during take-off and landing. Failure of a tire may not be readily apparent to the pilot or flight engineer, especially where several wheels are mounted on a common axle. The excessive loading that the failure of one tire puts on the remaining tires can cause other tires to fail, with severe consequences. Undue high pressure within a tire, such as caused by over inflation or excessive heating can lead to failure. If this high pressure can be monitored it may be possible to take remedial action to avoid failure of the tire or to reduce the effects of such a failure.
Measuring the pressure of a tire on a rotating wheel causes problems because of the need to make electrical connection between the rotating wheel and the static airframe. Various systems have been proposed to overcome this, such as, for example by using electrical inductive techniques. These previous systems suffer from several disadvantages. The large weight of previous systems is a disadvantage especially for large aircraft having many wheels each of which has a tire pressure monitor. The adverse environment has caused problems in providing systems capable of withstanding the vibration, shock, and centrifugal forces whilst still providing a measure of tire pressure of sufficient accuracy. Some previous systems rely on rotation of the wheel and are not capable of providing a reading while the wheel is stationary--this is a disadvantage since tire pressure cannot be checked prior to landing or while the aircraft is stationary prior to taxiing.
Some of these difficulties are also met when providing a tire pressure monitor for land vehicles.